1. Field of the Invention
The present invention relates in general to seats for motor vehicles and more particularly to seats of a shape-adjustable type which can change the shape of the seat to adjust to the physique of a seat occupant. More specifically, the present invention is concerned with the shape-adjustable seats of a type in which the shape change of the seat is achieved by controlling air pressure in various air-bags installed in the seat.
2. Description of the Prior Art
Hitherto, various shape-adjustable seats have been proposed and put into practical use particularly in the field of motor vehicles.
One of them is shown in Japanese Utility Model First Provisional Publication No. 59-195029. The seat of this publication uses a plurality of electric motors which, with an aid of a microcomputer, moves given portions of the seat. That is, when in use, an information on the height of the seat user is inputted to the computer. By processing the information, the computer controls the operation of the electric motors to provide the seat with a shape suitable for comfortably holding the occupant. The shape of the seat thus automatically but roughly provided can be accurately adjusted thereafter by operating a manual switch In this case, the accurately adjusted shape is memorized, and thus, thereafter, the accurately adjusted shape is automatically provided by the seat when the occupant uses the seat inputting his or her height information to the computer.
Another seat of the shape adjustable type is shown in Japanese Patent First Provisional Publication No. 61-257333. The seat of this publication employs a plurality of air-bags which are installed in given portions of the seat. By changing the air-pressure in each air-bag, the shape of the seat is changed. During a long time driving, a timer means operates to vary the air-pressure in the air-bags at regular intervals. With this, the pressure applied to given portions of the seat occupant by the air-bags is changed at regular intervals thereby lessening the fatigue of the seat occupant.
However, in the above-mentioned two conventional seats, the degree of fatigue of a seat occupant relative to his or her physique is given little thought. In fact, the physique of the seat occupant has a close relationship to the degree of fatigue as will be understood from the graphs of FIGS. 6 and 7.
That is, as is seen from FIG. 6, the degree of fatigue of the lumbar portion is higher in a slim person than in a overweight person. As seen from FIG. 7, the degree of the hip portion is higher in the overweight than in the slender person. This means that there is a positive correlation between the fatigue of an occupant and his or her physique.